Many current deflectable catheters include some form of locking device configured to retain a deflected portion of the catheter in the deflected orientation. In some examples, locking mechanisms and deflection mechanisms are separate from each other, thereby requiring dual controls and complicating use and manufacture of the catheter. For instance, the grip on the handle must be repeatedly readjusted to switch between actuating the locking mechanism and the deflection mechanism. Further, space in the handle must be set aside for separate locking and deflection mechanisms, thereby requiring tightly packed and complex handles or larger handles to accommodate the mechanisms.
Other examples of catheters include ratcheting teeth that prevent movement of a deflection control actuator in one direction while permitting movement of the actuator in another direction and corresponding continued deflection of the catheter. Ratcheting engagement of the actuator with the handle permits undesired deflection of the catheter, for example, where the catheter engages against vasculature during longitudinal movement of the catheter.
In still other examples, pull wires extend from the deflectable tip of a catheter shaft to the deflection control actuator, and the pull wires are not constrained from lateral movement within the handle. The pull wire may only be tensioned in one direction in this configuration thereby only allowing deflection in a single direction. Compression of the pull wire in another direction will buckle the wire and thereby substantially prevent active deflection of the catheter with the deflection control actuator. Straightening of the catheter in a direction opposed to that granted by tensioning the pull wire is thereby accomplished with the natural elasticity of the catheter distal tip. The deflected shaft exerts a passive pulling force on the pull wire that straightens the catheter without active control through the deflection control actuator. Further, the elasticity of the catheter only straightens the catheter and does not deflect the catheter in an opposed direction.
Additionally, in yet other examples, deflectable catheters include locking surfaces formed with the handle that substantially prevent adjustment of a range of travel for the deflection control actuator. For instance, the locking surfaces are formed along an interior surface of the handle. Changing the range of travel for the actuator requires redesigning the handle with a differently positioned locking surface. Multiple handle designs are therefore needed to accommodate desired ranges of travel for different catheter sizes, ranges of deflection and the like.
What is needed is a deflectable catheter that overcomes the shortcomings of previous designs. What is further needed is an easy to use deflectable catheter with locking and deflection functions that is not limited to passive deflection to straighten the catheter.